The present invention relates to switches and more particularly to novel change-over switches used in star-delta connection.
Heretofore, as switches used in three phase connection, particularly, star-delta connection, there are various types of switches such as knife switch, star-delta actuating switch or electromagnetic switch, but the knife switch is excellent as its structure is simple and performance is excellent. However, it is of bare type and moreover it not only generates arc when a circuit changing manipulation is made but also its manipulation must be done quickly and positively otherwise it is very dangerous, and poses a problem of security. Also, the star-delta actuating switch is of tumbler type requiring complicated connection work of terminals in its assembly. Each of these switches has a serious drawback that voltage is applied on the motor even if it is in the off condition. Moreover, since the electromagnetic switch is constructed by assembling two units of three pole electromagnetic switches as the star-delta switch, it not only becomes expensive but also, required large assembly space and moreover even in the off condition, the voltage is applied to the motor, the switch is not particularly suitable for use with 400 volts, and simultaneously, the mechanical locking is difficult which are the drawbacks of the electromagnetic switch.